HP FlexNetwork HSR6800 User manual

HPE FlexNetwork HSR6800 Routers
MPLS Configuration Guide
Part number:5998-4494R
Software version: HSR6800-CMW520-R3303P25
Document version: 6W105-20151231

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Contents
Configuring basic MPLS ·················································································1
Overview····························································································································································1
Basic concepts···········································································································································1
MPLS network structure·····························································································································2
LSP establishment and label distribution···································································································3
MPLS forwarding········································································································································5
LDP····························································································································································7
Protocols····················································································································································8
MPLS configuration task list·······························································································································9
Enabling the MPLS function·····························································································································10
Configuring a static LSP ··································································································································10
Configuration prerequisites······················································································································10
Configuration guidelines···························································································································10
Configuration procedure···························································································································11
Establishing dynamic LSPs through LDP ········································································································11
Configuring MPLS LDP capability············································································································11
Configuring local LDP session parameters······························································································12
Configuring remote LDP session parameters··························································································12
Configuring PHP ······································································································································13
Configuring the policy for triggering LSP establishment ··········································································14
Configuring the label distribution control mode························································································14
Configuring LDP loop detection ···············································································································15
Configuring LDP MD5 authentication·······································································································16
Configuring LDP label filtering··················································································································16
Maintaining LDP sessions································································································································18
Configuring BFD for MPLS LDP···············································································································18
Resetting LDP sessions···························································································································18
Managing and optimizing MPLS forwarding ····································································································18
Configuring MPLS MTU···························································································································19
Configuring a TTL processing mode for an LSR······················································································19
Sending back ICMP TTL exceeded messages for MPLS TTL expired packets ······································21
Configuring LDP GR ································································································································21
Configuring LDP NSR······························································································································23
Configuring MPLS statistics collection and reading·························································································24
Configuring MPLS statistics collection and reading (method 1)·······························································24
Configuring MPLS statistics collection and reading for specific LSPs (method 2)···································24
Inspecting LSPs···············································································································································24
Configuring MPLS LSP ping ····················································································································25
Configuring MPLS LSP tracert·················································································································25
Configuring BFD for LSPs························································································································25
Configuring periodic LSP tracert··············································································································26
Enabling MPLS trap·········································································································································27
Displaying and maintaining MPLS ···················································································································27
Displaying MPLS operation······················································································································27
Displaying MPLS LDP operation··············································································································29
Clearing MPLS statistics··························································································································30
MPLS configuration examples ·························································································································30
Configuring static LSPs····························································································································30
Configuring LDP to establish LSPs dynamically······················································································33
Configuring MPLS TE···················································································38
Overview··························································································································································38
Basic concepts·········································································································································39
MPLS TE implementation ························································································································39
CR-LSP····················································································································································40
CR-LDP····················································································································································41
RSVP-TE··················································································································································41

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Traffic forwarding ·····································································································································44
Automatic bandwidth adjustment·············································································································46
CR-LSP backup ·······································································································································46
FRR··························································································································································46
DiffServ-aware TE····································································································································47
MPLS LDP over MPLS TE·······················································································································49
Protocols and standards ··························································································································50
MPLS TE configuration task list·······················································································································51
Configuring basic MPLS TE·····························································································································51
Configuring DiffServ-aware TE ························································································································52
Creating an MPLS TE tunnel over a static CR-LSP·························································································53
Configuration prerequisites······················································································································53
Configuration guidelines···························································································································53
Configuration procedure···························································································································53
Configuring an MPLS TE tunnel with a dynamic signaling protocol·································································54
Configuring MPLS TE properties for a link·······························································································55
Configuring CSPF····································································································································56
Configuring RSVP-TE advanced features ·······································································································59
Configuring RSVP reservation style·········································································································59
Configuring RSVP state timers ················································································································60
Configuring the RSVP refresh mechanism ······························································································60
Configuring the RSVP hello extension·····································································································61
Configuring RSVP-TE resource reservation confirmation········································································61
Configuring RSVP authentication·············································································································62
Configuring DSCP for outgoing RSVP packets························································································62
Configuring RSVP-TE GR························································································································62
Configuring cooperation of RSVP-TE and BFD·······················································································63
Tuning CR-LSP setup······································································································································63
Configuring the tie breaker in CSPF ········································································································63
Configuring route pinning·························································································································64
Configuring administrative group and affinity attribute·············································································64
Configuring CR-LSP reoptimization·········································································································65
Tuning MPLS TE tunnel setup·························································································································65
Configuring loop detection ·······················································································································66
Configuring route and label recording······································································································66
Configuring tunnel setup retry··················································································································66
Assigning priorities to a tunnel·················································································································67
Configuring traffic forwarding···························································································································67
Forwarding traffic along MPLS TE tunnels using static routes·································································67
Forwarding traffic along MPLS TE tunnels using policy routing·······························································67
Forwarding traffic along MPLS TE tunnels through automatic route advertisement································68
Configuring traffic forwarding tuning parameters·····························································································70
Configuring the failed link timer················································································································70
Configuring automatic bandwidth adjustment··································································································71
Configuration guidelines···························································································································71
Configuration procedure···························································································································72
Configuring CR-LSP backup····························································································································72
Configuring FRR ··············································································································································73
Enabling FRR on the ingress node of a protected LSP ···········································································73
Configuring a bypass tunnel on its PLR···································································································74
Configuring node protection·····················································································································75
Configuring the FRR polling timer············································································································75
Inspecting an MPLS TE tunnel ························································································································76
Configuring MPLS LSP ping ····················································································································76
Configuring MPLS LSP tracert·················································································································76
Configuring BFD for an MPLS TE tunnel·········································································································76
Configuration guidelines···························································································································77
Configuration prerequisites······················································································································77
Configuration procedure···························································································································77
Configuring periodic LSP tracert for an MPLS TE tunnel·················································································78
Enabling MPLS TE statistics····························································································································78
Displaying and maintaining MPLS TE··············································································································79

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MPLS TE configuration examples····················································································································82
MPLS TE using static CR-LSP configuration example ············································································82
MPLS TE tunnel using RSVP-TE configuration example·········································································86
Inter-AS MPLS TE tunnel using RSVP-TE Configuration example··························································92
RSVP-TE GR configuration example·····································································································100
MPLS RSVP-TE and BFD cooperation configuration example······························································102
MPLS TE using CR-LDP configuration example····················································································104
CR-LSP backup configuration example·································································································111
FRR configuration example····················································································································114
IETF DS-TE configuration example ·······································································································123
MPLS LDP over MPLS TE configuration example·················································································130
MPLS TE in MPLS L3VPN configuration example·················································································136
Troubleshooting MPLS TE·····························································································································143
No TE LSA generated····························································································································143
Configuring MPLS L2VPN ··········································································144
Overview························································································································································144
Basic concepts of MPLS L2VPN············································································································144
MPLS L2VPN network models···············································································································144
Remote connection operation················································································································145
Local connection operation····················································································································146
Implementation of MPLS L2VPN ···········································································································147
VC types·················································································································································152
Control word···········································································································································153
VC redundancy ······································································································································154
MPLS L2VPN configuration task list ··············································································································154
Configuring basic MPLS L2VPN····················································································································155
Configuring a PE-CE interface·······················································································································155
Configuring the interface with PPP encapsulation·················································································156
Configuring the interface with HDLC encapsulation···············································································156
Configuring the interface with FR DLCI or FR port mode encapsulation···············································156
Configuring the interface with Ethernet encapsulation···········································································157
Configuring the interface with VLAN encapsulation···············································································157
Configuring the interface with transparent ATM AAL5 frame encapsulation··········································157
Configuring CCC MPLS L2VPN·····················································································································157
Configuring a local CCC connection······································································································157
Configuring a remote CCC connection ··································································································157
Configuring SVC MPLS L2VPN·····················································································································158
Configuring a static VC on a Layer 3 interface·······················································································159
Configuring primary and backup static VCs on a Layer 3 interface·······················································159
Configuring primary and backup static VCs for a service instance························································160
Configuring Martini MPLS L2VPN··················································································································161
Configuring the remote peer for a PE ····································································································162
Creating a Martini VC on a Layer 3 interface·························································································162
Creating a Martini VC for a service instance··························································································163
Configuring Kompella MPLS L2VPN ·············································································································164
Configuring BGP L2VPN capability········································································································164
Creating and configuring an MPLS L2VPN····························································································164
Creating a CE connection······················································································································165
Resetting L2VPN BGP sessions············································································································166
Displaying and maintaining MPLS L2VPN·····································································································167
MPLS L2VPN configuration examples···········································································································168
Example for configuring a local CCC connection···················································································168
Example for configuring a remote CCC connection···············································································170
Example for configuring SVC MPLS L2VPN with the VC type of PPP ··················································173
Example for configuring Martini MPLS L2VPN with the VC type of PPP···············································177
Example for configuring Martini VC redundancy····················································································181
Example for configuring Kompella MPLS L2VPN··················································································188
Example for configuring a Kompella local connection············································································190
Example for configuring a VC for a service instance ·············································································192
Troubleshooting MPLS L2VPN······················································································································196

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Configuring VPLS ·······················································································197
Overview························································································································································197
Operation of VPLS·································································································································197
VPLS packet encapsulation···················································································································200
H-VPLS implementation·························································································································200
Multi-hop PW··········································································································································202
VPLS configuration task list ···························································································································203
Enabling L2VPN and MPLS L2VPN ··············································································································203
Configuring static VPLS·································································································································204
Configuring a static VPLS instance········································································································204
Configuring LDP VPLS ··································································································································205
Configuring an LDP VPLS instance·······································································································206
Configuring BGP VPLS··································································································································207
Configuring the BGP extension··············································································································207
Configuring a BGP VPLS instance·········································································································207
Resetting VPLS BGP connections·········································································································208
Binding a VPLS instance ·······························································································································208
Binding a Layer 3 interface to a VPLS instance·····················································································208
Binding a service instance to a VPLS instance······················································································209
Configuring MAC address learning················································································································209
Configuring VPLS instance attributes ············································································································210
Displaying and maintaining VPLS··················································································································211
VPLS configuration examples························································································································212
Binding VPLS instances to service instances························································································212
Configuring VPLS instances ··················································································································217
Configuring H-VPLS with LSP access ···································································································220
Configuring PW redundancy for H-VPLS access···················································································223
Configuring BFD for the primary link in an H-VPLS network··································································227
Implementing multi-AS VPN through multi-hop PW···············································································231
Troubleshooting VPLS···································································································································236
Configuring MPLS L3VPN ··········································································237
Overview························································································································································237
MPLS L3VPN concepts··························································································································238
MPLS L3VPN packet forwarding············································································································240
MPLS L3VPN networking schemes·······································································································241
MPLS L3VPN routing information advertisement···················································································244
Inter-AS VPN··········································································································································245
Carrier's carrier ······································································································································248
Nested VPN ···········································································································································250
Multi-role host·········································································································································252
HoVPN···················································································································································252
OSPF VPN extension·····························································································································254
BGP AS number substitution and SoO··································································································257
MPLS L3VPN FRR·································································································································257
Multi-VPN-instance CE ··························································································································258
MPLS L3VPN configuration task list ··············································································································259
Configuring basic MPLS L3VPN····················································································································261
Configuration prerequisites····················································································································261
Configuring VPN instances····················································································································261
Configuring routing between a PE and a CE ·························································································265
Configuring routing between PEs···········································································································270
Configuring routing features for BGP VPNv4 subaddress family···························································271
Configuring soft GRE·····························································································································273
Configuring inter-AS VPN ······························································································································274
Configuring inter-AS option A·················································································································274
Configuring inter-AS option B·················································································································275
Configuring inter-AS option C ················································································································275
Configuring nested VPN ································································································································277
Configuring multi-role host·····························································································································278
Configuring and applying policy routing·································································································279

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Configuring a static route·······················································································································279
Configuring HoVPN········································································································································279
Configuring an OSPF sham link·····················································································································280
Configuring a loopback interface············································································································280
Redistributing the loopback interface route and OSPF routes into BGP················································280
Creating a sham link ······························································································································281
Configuring routing on an MCE······················································································································281
Configuring routing between an MCE and a VPN site···········································································282
Configuring routing between MCE and PE ····························································································286
Specifying the VPN label processing mode···································································································290
Configuring BGP AS number substitution and SoO·······················································································290
Configuring MPLS L3VPN FRR·····················································································································291
Resetting BGP connections···························································································································292
Displaying and maintaining MPLS L3VPN·····································································································292
MPLS L3VPN configuration examples···········································································································295
Configuring MPLS L3VPNs using EBGP between a PE and a CE························································295
Configuring MPLS L3VPNs using IBGP between a PE and a CE·························································302
Configuring an MPLS L3VPN that uses a GRE tunnel ··········································································309
Configuring a hub-spoke network ··········································································································314
Configuring inter-AS option A·················································································································322
Configuring inter-AS option B·················································································································326
Configuring inter-AS option C ················································································································331
Configuring carrier's carrier····················································································································337
Configuring nested VPN·························································································································344
Configuring multi-role host·····················································································································353
Configuring HoVPN································································································································355
Configuring OSPF sham links················································································································362
Configuring MCE····································································································································367
Configuring BGP AS number substitution······························································································371
Configuring BGP AS number substitution and SoO···············································································374
Example 1 for configuring MPLS L3VPN FRR·······················································································376
Example 2 for configuring MPLS L3VPN FRR·······················································································378
Configuring IPv6 MPLS L3VPN ··································································381
Overview························································································································································381
IPv6 MPLS L3VPN packet forwarding ···································································································381
IPv6 MPLS L3VPN routing information advertisement ··········································································382
IPv6 MPLS L3VPN network schemes and functions ·············································································382
IPv6 MPLS L3VPN configuration task list······································································································383
Configuring basic IPv6 MPLS L3VPN············································································································383
Configuring VPN instances····················································································································383
Configuring route related attributes for a VPN instance·········································································384
Configuring routing between a PE and a CE ·························································································387
Configuring routing between PEs···········································································································390
Configuring routing features for the BGP-VPNv6 subaddress family·····················································390
Configuring inter-AS IPv6 VPN······················································································································392
Configuring inter-AS IPv6 VPN option A································································································392
Configuring inter-AS IPv6 VPN option B································································································393
Configuring inter-AS IPv6 VPN option C································································································393
Configuring routing on an MCE······················································································································394
Configuring routing between an MCE and a VPN site···········································································395
Configuring routing between an MCE and a PE ····················································································398
Resetting BGP connections···························································································································401
Displaying information about IPv6 MPLS L3VPN ··························································································401
IPv6 MPLS L3VPN configuration examples···································································································402
Configuring IPv6 MPLS L3VPNs············································································································402
Configuring an IPv6 MPLS L3VPN that uses a GRE tunnel··································································410
Configuring inter-AS IPv6 VPN option A································································································414
Configuring inter-AS IPv6 VPN option C································································································419
Configuring carrier's carrier····················································································································425
Configuring MCE····································································································································432

vi
Document conventions and icons·······························································438
Conventions···················································································································································438
Network topology icons··································································································································439
Support and other resources ······································································440
Accessing Hewlett Packard Enterprise Support ····························································································440
Accessing updates·········································································································································440
Websites ················································································································································441
Customer self repair·······························································································································441
Remote support······································································································································441
Documentation feedback ·······················································································································441
Index···········································································································443

1
Configuring basic MPLS
Overview
Multiprotocol Label Switching (MPLS) enables connection-oriented label switching on
connectionless IP networks. It integrates both the flexibility of IP routing and the level of simplicity of
Layer 2 switching.
MPLS has the following advantages:
•MPLS forwards packets according to short- and fixed-length labels, instead of Layer 3 header
analysis and complicated routing table lookup, enabling highly-efficient and fast data forwarding
on backbone networks.
•MPLS resides between the link layer and the network layer. It can work over various link layer
protocols (for example, PPP,ATM, frame relay, and Ethernet), provide connection-oriented
services for various network layer protocols (for example, IPv4 and IPv6), and work with
mainstream network technologies.
•MPLS is connection-oriented and supports label stack. It can be used to implement various
functions, such as VPN, traffic engineering, and QoS.
Basic concepts
This section describes the basic concepts of MPLS.
FEC
MPLS groups packets with the same characteristics (such as packets with the same destination or
service class) into a class called a "forwarding equivalence class (FEC)." Packets of the same FEC
are handled in the same way on an MPLS network. The device supports classifying FECs according
to the network layer destination addresses.
Label
A label is a short, fixed length identifier for identifying a single FEC. A label is locally significant and
must be locally unique.
Figure 1 Format of a label
A label is encapsulated between the Layer 2 header and Layer 3 header of a packet. Alabel is four
bytes in length and consists of the following fields:
•Label—20 bits in length. Label value for identifying a FEC.
•Exp—Three bits in length. Reserved field, usually used for CoS.
•S—One bit in length. MPLS supports multiple levels of labels. This field indicates whether a
label is at the bottom of the label stack.A value of 1 indicates that the label is at the bottom of
the label stack.
•TTL—Eight bits in length. Like the homonymous IP header field, it is used to prevent loops.
Exp
0
S
19 2223 31
Label TTL
Layer 2 header Layer 3 headerLabel Layer 3 data

2
LSR
Alabel switching router (LSR) is a fundamental component on an MPLS network. LSRs support label
distribution and label swapping.
LER
Alabel edge router (LER) is an LSR that resides at the edge of an MPLS network and is connected to
another network.
LSP
A label switched path (LSP) is the path along which packets of a FEC travel through an MPLS
network.
An LSP is a unidirectional path from the ingress of an MPLS network to the egress. On an LSP, two
neighboring LSRs are called the "upstream LSR" and "downstream LSR," respectively. In Figure 2,
LSR B is the downstream LSR of LSRA, and LSR A is the upstream LSR of LSR B.
Figure 2 Diagram of an LSP
LFIB
Labeled packets are forwarded according to the label forwarding information base (LFIB).
Control plane and forwarding plane
An MPLS node consists of two planes, control plane and forwarding plane.
•The control plane assigns labels, selects routes, creates the LFIB, and establishes and
removes LSPs.
•The forwarding plane forwards packets according to the LFIB.
MPLS network structure
Figure 3 Diagram of the MPLS network structure

3
LSRs in the same routing or administrative domain form an MPLS domain.
An MPLS domain consists of the following types of LSRs:
•Ingress LSRs receive and label packets coming into the MPLS domain.
•Transit LSRs forward packets along LSPs to their egress LERs according to the labels.
•Egress LSRs remove labels from packets and forward the packets to their destination networks.
LSP establishment and label distribution
This section describes how MPLS sets up LSPs and distribute labels.
LSP establishment
Establishing LSPs is to bind FECs with labels on each LSR involved and notify its adjacent LSRs of
the bindings, so as to establish the LFIB on each LSR. LSPs can be manually established through
configuration, or dynamically established through label distribution protocols.
•Establishing a static LSP through manual configuration:
Static LSPs do not dynamically change in response to network topology changes, and are
suitable for small-scale, stable, and simple networks. To establish a static LSP, assign a label to
the FEC on each LSR along the packet forwarding path. Establishment of static LSPs
consumes fewer resources than dynamic LSP establishment.
•Establishing an LSP through a label distribution protocol:
Label distribution protocols are MPLS signaling protocols. They can classify FECs, distribute
labels, and establish and maintain LSPs. Label distribution protocols include protocols
designed specifically for label distribution, such as the Label Distribution Protocol (LDP), and
protocols extended to support label distribution, such as BGP and RSVP-TE.
This document discusses LDP only. For more information about LDP, see "LDP."
NOTE:
In this document, the term "label distribution protocols" refers to all protocols for label distribution.
The term "LDP" refers to the RFC 5036 LDP.
A dynamic LSP is established in the following procedure:
A downstream LSR classifies FECs according to destination addresses. It assigns a label to a FEC,
and distributes the FEC-label binding to its upstream LSR, which then establishes an LFIB entry for
the FEC according to the binding information. After all LSRs along the packet forwarding path
establish a LFIB entry for the FEC, an LSP is established for packets of this FEC.

4
Figure 4 Process of dynamic LSP establishment
Label distribution and management
An LSR informs its upstream LSRs of labels assigned to FECs through label advertisement. The
label advertisement modes include downstream unsolicited (DU) and downstreamon demand (DoD).
The label distribution control modes include independent and ordered.
Label management specifies the mode for processing a received label binding that is not useful at
the moment. The processing mode, called "label retention mode," can be either liberal or
conservative.
Figure 5 Label advertisement modes
As shown in Figure 5, the label advertisement modes include the DU mode and the DoD mode.
•In DU mode, an LSR assigns a label to a FEC and then distributes the FEC-label binding to its
upstream LSR without solicitation. The device supports only the DU mode.
•In DoD mode, an LSR assigns a label to a FEC and distributes the FEC-label binding to its
upstream LSR only when it receives a label request from the upstream LSR.
To establish an LSP, an upstream LSR and its downstream LSR must use the same label
advertisement mode.
Label distribution control modes include the independent mode and the ordered mode.
LSR A LSR B LSR D
LSR C
LSR E LSR F LSR G
LSR H
Ingress Egress
LSP
Label mapping
Egress
Transit
DU mode
DoD mode
2) Send a label request for the
FEC to the downstream.
3) Distribute a label mapping for
the FEC to the upstream upon
receiving the request.
Ingress
1) Unsolicitely distribute a label
mapping for a FEC to the upstream.
1) Send a label request for a FEC
to the downstream.
2) Unsolicitely distribute a label
mapping for the FEC to the
upstream.
4) Distribute a label mapping for
the FEC to the upstream upon
receiving the request.

5
•In independent mode, an LSR can distribute label bindings upstream at anytime. This means
that an LSR might have distributed a label binding for a FEC to its upstream LSR before it
receives a binding for that FEC fromits downstream LSR.As shown in Figure 6, in independent
label distribution control mode, if the label advertisement mode is DU, an LSR assigns labels to
its upstream even if it has not obtained labels from its downstream. If the label advertisement
mode is DoD, the LSR distributes a label to its upstream as long as it receives a label request
from the upstream.
Figure 6 Independent label distribution control mode
•In ordered mode, an LSR distributes its label binding for a FEC upstream only when it receives
a label binding for the FEC from its downstream or it is the egress of the FEC. In Figure 5, label
distribution control is in ordered mode. If the label advertisement mode is DU, an LSR
distributes a label upstream only when it receives a label binding for the FEC from its
downstream. If the label advertisement mode is DoD, after an LSR (Transit in this example)
receives a label request from its upstream (Ingress), the LSR (Transit) sends a label request to
its downstream (Egress). Then, after the LSR (Transit) receives the label binding from its
downstream (Egress), it distributes a label binding to the upstream (Ingress).
Label retention modes include the liberal mode and the conservative mode.
•In liberal mode, an LSR keeps any received label binding regardless of whether the binding is
from the next hop for the FEC or not. This mode allows for quicker adaptation to route changes
but wastes label resources because LSRs keep extra labels. The device supports only the
liberal mode.
•In conservative mode, an LSR keeps only label bindings that are from the next hops for the
FECs. This mode allows LSRs to maintain fewer labels but makes LSRs slower in adapting to
route changes.
MPLS forwarding
LFIB
An LFIB comprises the following table entries:
•Next Hop Label Forwarding Entry—NHLFE describes the label operation to be performed. It
is used to forward MPLS packets.
•FEC to NHLFE map—FTN maps each FEC to a set of NHLFEs at the ingress LSR. The FTN
map is used for forwarding unlabeled packets that need MPLS forwarding. When an LSR

6
receives an unlabeled packet, it looks for the corresponding FIB entry. If the Token value of the
FIB entry is not Invalid, the packet must be forwarded through MPLS. The LSR then looks for
the corresponding NHLFE entry according to the Token value to determine the label operation
to be performed.
•Incoming Label Map—ILM maps each incoming label to a set of NHLFEs. It is used to forward
labeled packets. When an LSR receives a labeled packet, it looks for the corresponding ILM
entry. If the Token value of the ILM entry is not null, the LSR looks for the corresponding NHLFE
entry to determine the label operation to be performed.
FTN and ILM are associated with NHLFE through Token.
MPLS data forwarding
Figure 7 MPLS forwarding process diagram
In an MPLS domain, a packet is forwarded in the following procedure:
1. Router B (the ingress LSR) receives a packet carrying no label. It determines the FEC of the
packet according to the destination address, and searches the FIB table for the Token value.
Because the Token value is not Invalid, Router B looks for the corresponding NHLFE entry that
contains the Token value. According to the NHLFE entry, Router B pushes label 40 to the
packet, and forwards the labeled packet to the next hop LSR (Router C) through the outgoing
interface (GigabitEthernet 1/0/2).
2. Upon receiving the labeledpacket, Router C looks for the ILM entry that contains the label 40 to
get the Token value. Because the Tokenvalue is not blank, Router C looks for the NHLFE entry
containing the Token value. According to the NHLFE entry, Router C swaps the original label
with label 50, and then forwards the labeled packet to the next hop LSR (Router D) through the
outgoing interface (GigabitEthernet 1/0/2).
3. Upon receiving the labeled packet, Router D (the egress) looks for the ILM entry according to
the label (50) to get the Token value. Because the Token is blank, Router D removes the label
from the packet. If the ILM entry records the outgoing interface, Router D forwards the packet
through the outgoing interface. If no outgoing interface is recorded, router D forwards the
packet according to the IP header of the packet.

7
PHP
In an MPLS network, when an egress node receives a labeled packet, it looks up the LFIB, pops the
label of the packet, and then performs the next level label forwarding or performs IP forwarding. The
egress node needs to do two forwarding table lookups to forward a packet: looking up the LFIB twice
or looking up the LFIB and the FIB once each.
The penultimate hop popping (PHP) feature can pop the label at the penultimate node to relieve the
egress of the label operation burden.
PHP is configured on the egress node. The label assigned by a PHP-capable egress node to the
penultimate hop can be one of the two listed:
•IPv4 explicit null label 0—The egress assigns an IPv4 explicit null label to a FEC and
advertises the FEC-label binding to the upstream LSR. When forwarding an MPLS packet, the
upstream LSR replaces the label at the stack top with the explicit null label and then sends the
packet to the egress. When the egress receives the packet, which carries a label of 0, it does
not look up for the LFIB entry but pops the label stack directly and performs IPv4 forwarding.
•Implicit null label 3—This label never appears in the label stack.An LSR directly performs a
pop operation to the labeled packets that match the implicit null labelrather than substituting the
implicit null label for the original label at the stack top. After that, the LSR forwards the packet to
the downstream egress LSR. The egress directly performs the next level forwarding upon
receiving the packet.
LDP
LDP establishes LSPs dynamically. Using LDP, LSRs can map network layer routing information to
data link layer switching paths.
Basic concepts of LDP
•LDP session—LDP sessions are established between LSRs over TCP connections to
exchange messages for label binding, label releasing, and error notification.
•LDP peer—Two LSRs using LDP to exchange FEC-label bindings are LDP peers.
LDP message type
LDP messages include the following types:
•Discovery messages—Declare and maintain the presence of LSRs.
•Session messages—Establish, maintain, and terminate sessions between LDP peers.
•Advertisement messages—Create, alter, and remove FEC-label bindings.
•Notification messages—Provide advisory information and notify errors.
LDP session, advertisement, and notification messages use TCP for reliability. Discovery messages
use UDP for efficiency.
LDP operation
LDP goes through the following phases in operation:
1. Discovery:
Each LSR sends hello messages periodically to notify neighboring LSRs of its presence. In this
way, LSRs can automatically discover their LDP peers. LDP provides the following discovery
mechanisms:
{Basic discovery mechanism—Discovers directly connected LSRs and establishes link hello
adjacencies with them. An LSR periodically sends LDPlink Hello messages to multicast address 224.0.0.2 that
identifies all routers on the subnet to advertise its presence.
{Extended discovery mechanism—Discovers indirectly connected LDP peers and establishes targeted
hello adjacencies.An LSR periodically sends LDP Hello messages to a given IP address so that the LSR with
the IP address can discover the LDP peer.

8
If two LSRs each have the same transport address (the source IP address used to establish a
TCP connection to the peer) for the basic and extended discovery mechanisms, the LSRs can
establish both a link hello adjacency and a targeted hello adjacency with each other, and the
two adjacencies are associated with the samesession. This method is suited for two LDP peers
that have both a direct link (only one hop) and an indirect link (more than one hop) in between.
It can protect the LDP session between the two peers and avoid LDP convergence upon failure
of one link. When the direct link fails, the link hello adjacency is deleted. In this case, if the
indirect link works correctly, the targeted hello adjacency remains. Therefore, the LDP session
is not deleted, and the FEC-label bindings based on this session are not deleted either. When
the direct link recovers, the LDP peers do not need to re-establish the LDP session or re-learn
the FEC-label bindings.
If two LSRs each have different transport addresses for the basic and extended discovery
mechanisms, only one type of hello adjacency (either link or targeted) can exist between them.
2. Session establishment and maintenance:
After an LSR finds a LDP peer, the LSRs go through the following steps to establish a session:
a. Establish a TCP connection between them.
b. Initialize negotiation of session parameters such as the LDP version, label advertisement
mode, and Keepalive interval.
After establishing a session between them, the two LDP peers send Hello and Keepalive
messages to maintain the session.
3. LSP establishment and maintenance:
LDP sends label requests and label binding messages between LDP peers to establish LSPs.
For the LSP establishment process, see "LSP establishment and label distribution."
4. Session termination:
An LSR terminates its LDP session with an LDP peer when:
{All Hello adjacencies deleted between the two peers.
LDP peers periodically send Hello messages to indicate that they intend to keep the Hello
adjacency. If an LSR does not receive any Hello message from a peer before theHello timer
expires, it deletes the Hello adjacency with this peer. An LDP session has one or more Hello
adjacencies. When the last Hello adjacency for the session is deleted, the LSR sends a
Notification message to terminate the LDP session.
{Loss of session connectivity.
An LSR determines the integrity of an LDP session according to the LDP PDU (which
carries one or more LDP messages) transmitted on the session. Before the Keepalive timer
times out, if two LDP peers have no information to exchange, they can send Keepalive
messages to each other to maintain the LDP session. If an LSR does not receive any LDP
PDU from its peer during a Keepalive interval, it closes the TCP connection and terminates
the LDP session.
{Receiving a shutdown message from the peer.
An LSR can also send a Shutdown message to its LDP peer to terminate the LDP session.
When receiving the Shutdown message from an LDP peer, an LSR terminates the session
with the LDP peer.
Protocols
•RFC 3031, Multiprotocol Label Switching Architecture
•RFC 3032, MPLS Label Stack Encoding
•RFC 5036, LDP Specification

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MPLS configuration task list
Task Remarks
Enabling the MPLS function Required.
Configuring a static LSP Required.
Use either the static
or dynamic LSP
configuration
method.
Establishing dynamic LSPs
through LDP
Configuring MPLS LDP capability Required.
Configuring local LDP session
parameters Optional.
Configuring remote LDP session
parameters Optional.
Configuring PHP Optional.
Configuring the policy for triggering
LSP establishment Optional.
Configuring the label distribution
control mode Optional.
Configuring LDP loop detection Optional.
Configuring LDP MD5
authentication Optional.
Configuring LDP label filtering Optional.
Maintaining LDP sessions Configuring BFD for MPLS LDP Optional.
Resetting LDP sessions Optional.
Managing and optimizing
MPLS forwarding
Configuring MPLS MTU Optional.
Configuring a TTL processing mode
for an LSR Optional.
Sending back ICMP TTL exceeded
messages for MPLS TTL expired
packets Optional.
Configuring LDP GR Optional.
Configuring LDP NSR Optional.
Configuring MPLS statistics
collection and reading
Configuring MPLS statistics
collection and reading (method 1) Optional.
Configuring MPLS statistics
collection and reading for specific
LSPs (method 2) Optional.
Inspecting LSPs
Configuring MPLS LSP ping Optional.
Configuring MPLS LSP tracert Optional.
Configuring BFD for LSPs Optional.
Enabling MPLS trap Optional.

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Enabling the MPLS function
In an MPLS domain, you must enable MPLS on all routers before you can configure other MPLS
features.
Before you enable MPLS, complete the following tasks:
•Configure link layer protocols to ensure the connectivity at the link layer.
•Assign IP addresses to interfaces so that all neighboring nodes can reach each other at the
network layer.
•Configure static routes or an IGP protocol for the LSRs to communicate with each other.
To enable MPLS:
Step Command Remarks
1. Enter system view. system-view N/A
2. Configure the MPLS LSR ID. mpls lsr-id lsr-id
By default, no MPLS LSR ID is
configured.
An MPLS LSR ID is in the format
of an IP address and must be
unique within an MPLS domain.
As a best practice, use the IP
address of a loopback interface
on an LSR as the MPLS LSR ID.
3. Enable MPLS globally and
enter MPLS view. mpls By default, global MPLS is
disabled.
4. Return to system view. quit N/A
5. Enter interface view. interface interface-type
interface-number N/A
6. Enable MPLS for the
interface. mpls By default, MPLS is disabled on
interfaces.
Configuring a static LSP
The principle of establishing a static LSP is that the outgoing label of an upstream LSR is the
incoming label of its downstream LSR.
Configuration prerequisites
Before you configure a static LSP, complete the following tasks:
•Determine the ingress LSR, transit LSRs, and egress LSR for the static LSP.
•Enable MPLS on all these LSRs.
•Make sure the ingress LSR has a route to the FEC destination. This is not required on the
transit LSRs and egress LSR.
Configuration guidelines
Follow these guidelines when you configure a static LSP:
•Do not specify a P2MP interface (such as a P2MP-type ATM subinterface or frame relay
subinterface) as the outgoing interface. Otherwise, the static LSP cannot be up.

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•On the ingress LSR, the specified next hop or outgoing interface must be consistent with the
next hop or outgoing interface of the optimal route in the routing table. If you configure a static
IP route for the LSP, be sure to specify the same next hop or outgoing interface for the static
route and the static LSP. For information about configuring a static IP route, see Layer 3—IP
Routing Configuration Guide.
•For an ingress or transit LSR, do not specify the public address of an interface on the LSR as
the next hop address.
Configuration procedure
To configure a static LSP:
Step Command
7. Enter system view. system-view
8. Configure a static LSP taking the current LSR
as the ingress.
static-lsp ingress lsp-name destination dest-addr
{ mask | mask-length } { nexthop next-hop-addr |
outgoing-interface interface-type
interface-number } out-label out-label
9. Configure a static LSP taking the current LSR
as a transit LSR.
static-lsp transit lsp-name incoming-interface
interface-type interface-number in-label in-label
{ nexthop next-hop-addr | outgoing-interface
interface-type interface-number } out-label out-label
10. Configure a static LSP taking the current LSR
as the egress. static-lsp egress lsp-name incoming-interface
interface-type interface-number in-label in-label
Establishing dynamic LSPs through LDP
Perform the tasks in this section so the device can use LDP to set up dynamic LSPs.
Configuring MPLS LDP capability
Step Command Remarks
1. Enter system view. system-view N/A
2. Enable LDP capability globally and
enter MPLS LDP view. mpls ldp Not enabled by default.
3. Configure the LDP LSR ID. lsr-id lsr-id
Optional.
By default, the LDP LSR ID is the
same as the MPLS LSR ID.
You need to perform this task only
in a multi-VPN context to make
sure that different LDP instances
have different LDP LSR IDs if
their address spaces overlap.
Otherwise, TCP connections
cannot be established.
4. Return to system view. quit N/A
5. Enter interface view. interface interface-type
interface-number N/A

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Step Command Remarks
6. Enable LDP capability for the
interface. mpls ldp Not enabled by default.
NOTE:
Disabling LDP on an interface terminates all LDP sessions on the interface. As a result, all LSPs
using the sessions are deleted.
Configuring local LDP session parameters
LDP sessions established between localLDP peers are local LDPsessions. To establish a local LDP
session:
•Determine the LDP transport addresses of the two peers and make sure that the LDP transport
addresses are reachable to each other. This step is to establish the TCP connection.
•If many LDP sessions exist between the two LSRs or the CPU is occupied much, you must
adjust timers to ensure the stability of the LDP sessions.
To configure local LDP session parameters:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter interface view. interface interface-type
interface-number N/A
3. Set the link Hello timer. mpls ldp timer hello-hold value Optional.
15 seconds by default.
4. Set the link Keepalive timer. mpls ldp timer keepalive-hold
value
Optional.
45 seconds by default.
5. Configure the LDP transport
address. mpls ldp transport-address
{ ip-address | interface }
Optional.
The default takes the value of the
MPLS LSR ID.
The specified IP address must be
the IP address of an interface on
the device.
Configuring remote LDP session parameters
LDP sessions established between remote LDP peers are remote LDP sessions. Remote LDP
sessions aremainly used in Martini MPLS L2VPN, Martini VPLS, and MPLS LDP over MPLS TE. For
more information about remote session applications, see "Configuring MPLS L2VPN," "Configuring
VPLS," and "Configuring MPLS TE."
To establish a remote LDP session, perform the following operations:
•Determine the LDP transport addresses of the two peers and make sure the LDP transport
addresses are reachable to each other. Do this to establish the TCP connection.
•If many LDP sessions exist between the two LSRs or the CPU is occupied often, adjust timers
to ensure the stability of the LDP sessions.
To configure remote LDP session parameters: